1. Field of the Invention
The subject of this invention is an improved method for cutting metal, in which method an electric arc is formed between the metal and the cutting torch, the cutting being achieved by simultaneously blowing gas into the cut.
2. Description of the Prior Art
Known methods of cutting based on the use of an electric arc include the TIG and MIG methods, in which the cutting effect of the arc is achieved with the help of a powerful blast of gas. The TIG method employs an electrode which is fixed in the cutting torch. In the MIG method the electrode is a metal wire which is continuously fed through the torch towards the point of cutting. The arc is best struck by bringing the electrode and the metal being cut, which acts as the opposite pole, into contact with each other.
The performance of the known arc cutting methods mentioned above is satisfactory when the cutting can be carried out in good outdoor conditions. In difficult conditions, however, as, for example, when the cutting is performed underwater, these methods are inconvenient and ineffectual. It is not possible be these methods, for instance, to cut several layers of thick metal plates; this is a consequence of the cooling effect of the cold water which penetrates the cut. For this reason, when it is necessary to carry out cutting work underwater, as in connection with repair work on ships, oil-drilling platforms and underwater pipelines, a gas cutting method has been used which is based on melting and burning the metal using oxygen and a liquid fuel, such as petrol. A disadvantage of this method, however, is that considerable quantities of the fuel rise to the surface of the water where they constitute an explosion hazard.